Parameters common to all provisioners:

- `pause_before` (duration) - Sleep for duration before execution.

- `only` (array of string) - Only run the provisioner for listed builder(s)
  by name.

- `override` (object) - Override the builder with different settings for a
  specific builder, eg :

  ```json
  {
    "type": "shell",
    "script": "script.sh",
    "override": {
      "vmware-iso": {
        "execute_command": "echo 'password' | sudo -S bash {{.Path}}"
      }
    }
  }
  ```

- `timeout` (duration) - If the provisioner takes more than for example
  `1h10m1s` or `10m` to finish, the provisioner will timeout and fail.
